Modern surgical procedures often necessitate localized diagnoses, or treatments applied to relatively inaccessible interior areas of the body. In the past, such procedures typically involved invasive surgery, enabling the physician to visually identify or treat the area of interest by accessing a relatively large opening or incision made in the body. Unfortunately, invasive surgical methods often include undesirable side-effects from the tissue trauma associated with the procedure. Often, the effects of the trauma prolong the healing and rehabilitation period for the patient.
To minimize the trauma often associated with invasive surgery, those skilled in the art have developed relatively small catheters for insertion into the vasculature of the body. Typically, the catheter accesses the body through a small incision made near the skin, where it can then be advanced to an area of interest. However, in order to navigate through the vasculature in a predictable manner, the catheter must be precisely controllable to position, as examples, ablation electrodes or imaging probes proximate specific tissues of interest.
To enable catheter manipulation inside the body, slidable control wire mechanisms are used to selectively "steer" the distal tip of the catheter while the operator inserts the device into the body. Such mechanisms typically include a pair of control wires that span the length of the catheter shaft, or body. The control wires have respective distal ends anchored to specific locations at the distal tip of the catheter body corresponding to predetermined deflectional movement. The proximal ends of the wires are mounted to a slider mechanism that responds to the operator to place one of the wires in tension, pulling at the catheter end for deflection in a first direction, while simultaneously compressing, or buckling, the other wire. An example of such a catheter configuration incorporating such a control mechanism may be found in U.S. Pat. No. 5,383,852, assigned to the assignee of the present invention.
While such devices generally provide a relatively high degree of directional deflection for the catheter tip, over a relatively short period of time the repetitive tensioning and buckling of the control wires often causes premature control wire fatigue. As a result, the operable lifespan of the device may be substantially shortened.
To address the problem of wire fatigue in a steerable medical device, one proposal (Takahashi U.S. Pat. No. 4,294,233) discloses steering the distal tip of an endoscope by independently manipulating two pull cables by turning an operating dial shaft. Means are provided for absorbing the slack, or buckled portion of the non-tensioned wire. The disclosed means include a long groove portion inside a slack absorbing member to define an escape area for the non-steered cable.
While this design may be satisfactory for its intended applications in the area of rotatable control mechanisms, it fails to address the slack absorption problem for slidable control mechanisms. Many operators prefer linearly displaceable sliding control mechanisms in particular applications. Moreover, the Takahashi design provides only a passive device to minimize compression on the non-selected cable.
Therefore, those skilled in the art have recognized the need for a slidable control mechanism for manipulating the distal end of a steerable catheter. Additionally, the need exists for a slidable control mechanism to actively assist in preventing compression on either steering cable. The control mechanism of the present invention satisfies these needs.